Vitamin-D- PRODH- & DTNBP1-Induced Hyperprolinemia:Schizophrenia Risk & Treatment

描述（由申请人提供）：已知精神分裂症（SZ）的最高遗传风险是由染色体22q11的半合子微缺失引起的。脯氨酸脱氢酶基因（PRODH）位于常见缺失区，编码催化脯氨酸分解代谢的酶。脯氨酸是谷氨酸能突触的神经调节剂，由PRODH突变或包含PRODH的cnv引起的外周高脯氨酸血症与认知障碍和智商下降有关。我们最近报道了高脯氨酸血症与SZ的高度显著关联。我们现在提供的证据表明，另外两个独立的SZ危险因素：维生素d水平低和异常结合蛋白基因（Dtnbp1）突变，也会导致高脯氨酸血症。我们的研究结果表明，由维生素d和DTNBP1调节的生物学途径通过PRODH表达的丧失而趋同，脯氨酸升高是常见的SZ内表型。研究已经证明了高脯氨酸血症的功能失调后果，如谷氨酸能和多巴胺信号异常导致认知缺陷和脉冲前抑制（PPI）减弱。因此，在Dtnbp1模型中靶向高脯氨酸血症可能对神经递质信号传导和功能恢复产生积极影响。本研究的目的是在以下具体目标下检验我们的假设。目的1：测试低维生素D、PRODH和DTNBP1基因变异对SZ相关高脯氨酸血症的相对分子贡献。在SZ患者和对照样本（n=250）中，我们将测量血浆脯氨酸和维生素d水平，证实脯氨酸升高和维生素d低之间的密切关系。根据我们的初步数据，我们预计80%的高脯氨酸血症是由维生素d含量低引起的，而DTNBP1和PRODH变体将导致剩余的20%。因此，我们将对我们完整的研究队列（404名受试者）进行分子分析，筛选改变基因表达的PRODH和DTNBP1变异，并测试变异与脯氨酸升高的结果之间的关联，以及与低维生素d的相互作用。目的2：探讨Dtnbp1模型中导致高脯氨酸血症的分子途径。目标2。分子分析将包括检测Prodh、p53调控基因和Comt （Prodh的下游）的外周和中枢神经系统组织表达，以及皮质、海马和外周脯氨酸水平。目标2 b。利用sdy-/-和Prodh+/-小鼠的原代神经元和星形胶质细胞，我们将通过维生素D和噻唑烷二酮类药物罗格列酮（RZG）治疗，直接上调Prodh的表达，测试Prodh表达的恢复和细胞脯氨酸的减少。目的3：在体内Dtnbp1模型中靶向高脯氨酸血症。我们将研究是否用维生素D （Aim 3a）、RZG （Aim 3b）治疗，以及为了寻求减少脱靶效应的影响，与单独的载体治疗相比，脯氨酸缺乏饮食（Aim 3c）在体内恢复上述途径，并预防或减轻Sdy-/-缺陷，例如PPI和空间工作记忆。

DESCRIPTION (provided by applicant): The highest known genetic risk of schizophrenia (SZ) is conferred by hemizygous microdeletion of chromosome 22q11. The proline dehydrogenase gene (PRODH) is located in the common deleted region, and encodes the enzyme that catalyzes proline catabolism. Proline is a neuromodulator at glutamatergic synapses, and the peripheral hyperprolinemia arising from PRODH mutations or CNVs encompassing PRODH, has been associated with cognitive impairment and decreased IQ. We recently reported a highly significant association of hyperprolinemia with SZ. We now provide evidence that two further independent SZ risk factors: Low vitamin-D status, and mutation of the dysbindin gene (Dtnbp1), also cause hyperprolinemia. Our findings suggest convergence of the biological pathways regulated by vitamin-D and DTNBP1, via loss of PRODH expression, with elevated proline as a common SZ endophenotype. Studies have documented the dysfunctional consequences of hyperprolinemia, such as aberrant glutamatergic and dopamine signaling leading to, for example, cognitive deficits and attenuated prepulse inhibition (PPI). Targeting hyperprolinemia in the Dtnbp1 model may therefore positively impact neurotransmitter signaling and restore function. This proposed study is designed to test our hypotheses under the following Specific Aims. Aim 1: To test the relative molecular contributions of low Vitamin D, and PRODH, and DTNBP1 gene variants, to SZ- associated hyperprolinemia. In a SZ patient and control sample (n=250), we will measure plasma proline and Vitamin-D levels, confirming the strong relationship between elevated proline and low Vitamin-D. From our preliminary data, we anticipate that 80% of the measured hyperprolinemia will arise from low vitamin-D, while DTNBP1 and PRODH variants will be responsible for the remaining 20%. Thus, we will perform molecular analyses on our complete study cohort (404 subjects), screening for PRODH, and DTNBP1 variants that alter gene expression, and testing for variant associations, plus interactions with low Vitamin-D, on the outcome of proline elevation. Aim 2: To examine the molecular pathway leading to hyperprolinemia in the Dtnbp1 model. Aim 2A. Molecular analyses will include assay of peripheral and CNS tissue expression of Prodh, p53 regulated genes, and Comt (downstream of Prodh), as well as of cortical, hippocampal and peripheral proline levels. Aim 2B. Utilizing primary neurons and astrocytes from sdy-/- and Prodh+/- mice, we will directly upregulate Prodh expression, via treatment with Vitamin D and the thiazolidinedione drug Rosiglitazone (RZG), testing for restoration of Prodh expression and decreased cellular proline. Aim 3: To target hyperprolinemia in the Dtnbp1 model in vivo. We will examine whether treatment with Vitamin D (Aim 3a), RZG (Aim 3b), and, to seek to reduce the impact of off-target effects, a proline-deficient diet (Aim 3c), compared to vehicle- treatment alone, restores the above pathway in vivo, and prevents or alleviates the Sdy-/- deficit in, for example, PPI and spatial working memory.